In a non-magnetic medium, such as a fluid, in which magnetic particles are dispersed, a measurement of the magnetic properties has been used to determine parameters, such as the magnetic particle concentration, in the medium. In the prior art, the response of the medium to the application of a magnetic field to a fluid has been used to measure the properties of magnetic particles suspended therein and, consequently, to determine the properties of fluid itself. In U.S. Pat. No. 4,651,092, entitled METHOD OF DETERMINING DISPERSION OF VISCOSITY OF RESIN/SOLVENT MIXTURE CONTAINING MAGNETIC PARTICLES, issued on Mar. 17, 1987 in the name of A. Brunsch et al., a magnetic field generated by a set of coils is applied to fluid to determine characteristics of magnetic particles suspended in a fluid medium, for example, the concentration of magnetic particles in the medium. In the configuration disclosed, a relatively small magnetic field (approximately 10 Oe) is generated and applied to the material under test. In U.S. Pat. No. 4,522,501, entitled MONITORING MAGNETICALLY PERMEABLE PARTICLES IN ADMIXTURE WITH A FLUID CARRIER, issued on Jun. 11, 1985 in the name of M. A. Shannon, the concentration of magnetic particles in a fluid medium is determined by measuring the change in torque in a rotating conducting member resulting from the eddy current variation when the fluid medium is used to shield the rotating member from an applied magnetic field. Neither of the references provides the requisite accuracy for the determination of the magnetic properties of the magnetic medium.
Apparatus is commercially available for measuring the magnetic properties of a material. For example, Model 7600A BH Meter available from LDJ Incorporated is a microprocessor-controlled device for the measurement of magnetic properties of materials. Such devices are expensive and typically can measure parameters which, in many situations are not important for characterization of the material.
A need has therefore been felt for apparatus and an associated method for measuring the dispersion or the magnetic saturation of a fluid having magnetic particles suspended therein; apparatus which is relatively simple, accurate, and which does not involve undue complexity.